Photovoltaic solar cells can be improved through the use of concentrators, which collect sunlight in a large area and present it in a much smaller area. This can both increase the efficiency of the solar cells and reduce the required area of the cells.
The simplest solar concentrator is a focusing lens or mirror, which increases the light intensity on the solar cell. Traditional optics limits the distance from the focusing lens or mirror to the focal spot to be no less than approximately the characteristic dimension of the focusing element (for example, the diameter of a lens with circular aperture). Large concentration, then, results in a large concentrator using traditional optics.
Accordingly, there is a need for optical concentrators that are thinner (smaller in the direction perpendicular to the concentrator surface) and lighter than permitted by traditional optics.